Photoelectric web defect-detecting apparatus which provides for overcoming the ray-diverging effect of roller curvature

ABSTRACT

Apparatus for optically detecting imperfections on the surface of a web which is being advanced on a roller. The apparatus comprises a light source for directing light rays onto the surface of the web on the roller, a lens assembly disposed between the light source and the roller for directing parallel light rays toward the web surface, and an optical system for directing the reflected light rays to a photoconductive element.

United States Patent Inventor Fumio Sugaya Kanagawa, Japan Appl. No. 802,946

Filed Feb. 27, 1969 Patented June 29, 1971 Assignee Fuji Photo Film Co., Ltd.

Kanagawa, Japan Priority Feb. 27, 1968 Japan 43/11961 PHOTOELECTRIC WEB DEFECT-DETECTING APPARATUS WHICH PROVIDES FOR OVERCOMING THE RAY-DIVERGING EFFECT OF ROLLER CURVATURE 3 Claims, 4 Drawing Figs.

US. Cl

250/219 Int. Cl G0ln 21/16, GOln 21/32 250/219 Field 0! Search DF, 219 WE; 356/200 [56] References Cited UNITED STATES PATENTS 2,371,963 3/1945 La Pierre 250/219 2,487,51 l 1 1/1949 Bedford 250/219 X 3,117,182 1/1964 Hell etaL 250/219UX 3,206,606 9/1965 Burgo et al. 250/219 3,410,643 1 1/1968 Jorgensen 356/200 Primary Examiner-James W Lawrence Assistant Examiner-T. N. Grigsby Attorney-Sughrue, Rothwell, Mion, Zinn & Macpeak ABSTRACT: Apparatus for optically detecting imperfections on the surface of a web which is being advanced on a roller. The apparatus comprises a light source for directing light rays onto the surface of the web on the roller, a lens assembly disposed between the light source and the roller for directing parallel light rays toward the web surface, and an optical system for directing the reflected light rays to a photoconductive element.

PATENTED JUN29 I97! 35-89817 sum 1 or 2 FIG. 2

no.4 IN VENTOR FUMIO SUGAYA M Ma ATTORNEYS PATENTEUJUNZSIQYI 3589.817

sum 2 0F 2 INVENTOR FUMIO SUGAYA A'ITOR NEYK PHOTOELECTRIC WEB DEFECT-DETECTING APPARATUS WHICH PROVIDES FOR OVERCOMING THE RAY-DIVERGING EFFECT OF ROLLER CURVATURE BACKGROUND OF THE INVENTION l. Field of the Invention The present invention relates to a method and apparatus for detecting imperfections on the surface of a web by optical means.

I 2. Description of the Prior Art There have been in general three types of detecting devices for detecting imperfections on a web, both of which methods employ reflected and transmitted light. The three types are as follows; a type in which a number of photoconductive elements are arranged laterally adjacent to the advancing web, a type called the flying spot method" in which a light spot is swept in the effective site field of a photoconductive element, and a type called the "flying image method" in which the portion to be detected is uniformly illuminated and a point thereon corresponding to the site field of a photoconductive element is swept.

These devices for detecting imperfections are used in general to provide signals of the imperfections to an automatic cutter to cut out and remove the cut portion containing the imperfection. Otherwise, the above devices are used for marking the web to indicate the imperfection or for recording the condition of the imperfection on the web.

SUMMARY OF THE INVENTION A semicylindrical lens is provided for making the illuminating light rays parallel with one another. Another semicylindrical lens is also provided for concentrating the parallel light rays onto the portion of the surface of the web to be checked for imperfections. The light rays reflected from the surface of the web are detected by a photoconductive element using the flying image method. 7

As described above, the conventional method of the flying image" has been to employ uniform illumination of the web. Therefore, when an imperfection has been illuminated by rays from various directions, the reflected light rays from the imperfection which reached the photoconductive element have been an extremely small part of the total number of rays from the reflected imperfection. This method has been disadvantageous from the point of view of efficiency and the resolution of power. In accordance with the present invention, the imperfection on the moving web is illuminated by parallel light rays and as a result high efficiency in resolving power are achieved.

It is a principal object of the present invention to provide an improved method for effectively detecting imperfections on the moving web such as unevenness and scratches which ex-' tend in a direction parallel to the advancing direction of the web. It is another object of the present invention to provide an effective apparatus for detecting imperfections on the moving web.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a perspective view of an embodiment of the detecting apparatus in accordance with the present invention.

FIG. 2 is a perspective view of an example of the detecting device which is exemplary of the prior art.

FIG. 3 is a perspective view of the main part of the detecting device in accordance with the present invention.

FIG. 4 is a cross-sectional view of the main part of the detecting device shown in FIG. 3 in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, as best shown in FIG. 1, il-

lustrating an embodiment of the present invention, the

reference character 1 denotes a light source such as a tungsten lamp including a linear filament. The reference numeral 2 denotes an infrared filter to be used in the event the device is used to detect imperfections on the surface of a photosensitive photographic film. Numeral 3 denotes a first semicylindrical lens for making the emitted light rays from the light source 1 parallel with one another and projecting them perpendicular to the portion 5 to be detected on the web 6. The lens 3 may be spherical. The reference character 4 denotes a second semicylindrical lens for concentrating the parallel rays formed by the first semicylindrical lens 3 onto the surface of the web 6 in the shape of a wedge. The effect of the second lens 4 will be described in detail referring to FIG. 4. The reference numeral 7 denotes a roller for rolling the web in a predetermined position. Numeral 8 denotes a lens for concentrating the reflected parallel light rays from the detected portion 5 onto a mirror 10 which is vibrated. Numeral 9 denotes a spherical lens for focusing the image of the detected portion 5. Numeral l0 denotes a vibrating mirror for scanning the detected portion 5 which corresponds to the site field of the photoconductive element 15. The vibrating mirror 10 is driven by means of a magnet 11 and a coil 12.

The coil 12 is connected to an oscillator 13 in the present invention. The vibrating mirror 10 vibrates at a frequency of, for example, 200 cycles per second. Accordingly, the site field of the photoconductive element 15 reciprocates on the portion of the surface of the web 6 to be detected at a speed of 200 times per second. The vibrating mirror 10 can be replaced by a rotating multifaced mirror, but in this case, a complicated device is required to obtain the results since the illuminating light is cut out at the end of the detected portion 5 or at the end of the lenses 4 and 8 and therefore, a clamp device is required for eliminating the signal. The signal from the photoconductive element 15 is amplified by the amplifier 16. The amplifier 16 is constructed having a high pass filter and a low-pass filter in order to separate the signals of sharp imperfections such as scratches from the signals of relatively mild imperfections such as unevenness. The amplifier 16 can detect the two kinds of imperfections with different sensitivity. The reference numeral 17 denotes a discriminating circuit which transmits a signal to the memory circuit 18 when a signal of a level higher than a reference level is provided at the input thereof. The memory circuit 18 memorizes the signal until the web is cut off at the portion of the web having the imperfection detected by the above device which includes circuit 17. A solenoid is energized to take out the portion of the web having the imperfection detected. Alternatively, the memory circuit 18 memorizes the signal until the portion of the web having the imperfection comes up to the position to be marked and then energizes the marking solenoid.

Referring now to FIGS. 2, 3 and 4, illustrating in more detail the feature of the present invention, wherein FIG. 2 illustrates a conventional illuminating method wherein the detected portion of the web is uniformly illuminated over a broad range with a lamp 19. If imperfection 20 passes, the light value of the light ray 21 directed to the photoconductive element varies, however, the variation of. the light value is very small because the detected portion is illuminated from various directions.

However, if the light rays directed onto the detecting portion of the web are parallel with one another as shown in FIG. 3, the shade caused by the imperfection is seen immediately and the variation of light value of the light rays 21 reaching the photoconductive element is greater.

As shown in FIG. 4, by arranging the semicylindrical lens 4 so as to position the focal point 23 thereof ahead of the detected portion 5, most of the light rays concentrated in the wedge shape are directed in the same direction, because the surface of the detected portion of the web is curved along the cylindrical surface of the roller 7. Moreover, by positioning the focal point of the cylindrical lens 4 on the roller 7 and beyond the detected portion 5, in the manner shown in FIG. 4, the detected portion 5 on the surface of the web becomes an elongated band having a width such that most of the light rays directed to the detected portion are used effectively. Therefore, there is no unevenness in the detecting sensitivity such as that caused by missing a scan between successive scans, and the light rays are effectively used. This latter advantage is particularly useful for aweb which is to be free from exposure to light rays such as a web of photographic material.

The invention has been described in detail with particular reference to the preferred embodiment thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

What I claim is:

1. man apparatus for detecting the imperfections on the surface of a web wherein a roller is provided for feeding the web, a light source is provided for directing the light rays onto the surface of the web which moves along the roller, and an optical system is provided for directing the reflected light rays from the surface of the web to a photoconductive element; the

improvement comprising a first lens disposed between said light source and said roller for making said light rays from said light source parallel with one another, and a second lens disposed between said first lens and said roller for concentrating the parallel rays formed by said first lens onto the web surface in the form of a wedge, the focal point of said second lens being positioned beyond the surface of the web on the roller so that most of the light rays will be reflected in the same direction.

2. The apparatus of claim 1 wherein said optical system comprises a vibrating mirror, and a third lens disposed near said roller for directing the reflected light rays toward said vibrating mirror, said vibrating mirror directing the reflected light rays toward said photoconductive element.

3. The apparatus of claim 2 further comprising an amplifier, a discriminating circuit and a memory circuit connected to said photoconductive element. 

1. In an apparatus for detecting the imperfections on the surface of a web wherein a roller is provided for feeding the web, a light source is provided for directing the light rays onto the surface of the web which moves along the roller, and an optical system is provided for directing the reflected light rays from the surface of the web to a photoconductive element; the improvement comprising a first lens disposed between said light source and said roller for making said light rays from said light source parallel with one another, and a second lens disposed between said first lens and said roller for concentrating the parallel rays formed by said first lens onto the web surface in the form of a wedge, the focal point of said second lens being positioned beyond the surface of the web on the roller so that most of the light rays will be reflected in the same direction.
 2. The apparatus of claim 1 wherein said optical system comprises a vibrating mirror, and a third lens disposed near said roller for directing the reflected light rays toward said vibrating mirror, said vibrating mirror directing the reflected light rays toward said photoconductive element.
 3. The apparatus of claim 2 further comprising an amplifier, a discriminating circuit and a memory circuit connected to said photoconductive element. 